[PATCH v29 19/32] mm/mmap: Add shadow stack pages to memory accounting

Yu-cheng Yu
2021-08-20T18:20:57Z

Account shadow stack pages to stack memory.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Kees Cook <keescook@chromium.org>
---
v26:
- Remove redundant #ifdef CONFIG_MMU.

v25:
- Remove #ifdef CONFIG_ARCH_HAS_SHADOW_STACK for is_shadow_stack_mapping().

v24:
- Change arch_shadow_stack_mapping() to is_shadow_stack_mapping().
- Change VM_SHSTK to VM_SHADOW_STACK.
---
arch/x86/include/asm/pgtable.h | 3 +++
arch/x86/mm/pgtable.c | 5 +++++
include/linux/pgtable.h | 7 +++++++
mm/mmap.c | 5 +++++
4 files changed, 20 insertions(+)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index bfe4ea2b652d..0983a91b464c 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1638,6 +1638,9 @@ static inline bool arch_faults_on_old_pte(void)
#define maybe_mkwrite maybe_mkwrite
extern pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma);

+#define is_shadow_stack_mapping is_shadow_stack_mapping
+extern bool is_shadow_stack_mapping(vm_flags_t vm_flags);
+
#endif /* __ASSEMBLY__ */

#endif /* _ASM_X86_PGTABLE_H */
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index c22c8e9c37e8..61a364b9ae0a 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -884,3 +884,8 @@ int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)

#endif /* CONFIG_X86_64 */
#endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */
+
+bool is_shadow_stack_mapping(vm_flags_t vm_flags)
+{
+ return vm_flags & VM_SHADOW_STACK;
+}
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index e24d2c992b11..71aa63e2b014 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1484,6 +1484,13 @@ static inline bool arch_has_pfn_modify_check(void)
}
#endif /* !_HAVE_ARCH_PFN_MODIFY_ALLOWED */

+#ifndef is_shadow_stack_mapping
+static inline bool is_shadow_stack_mapping(vm_flags_t vm_flags)
+{
+ return false;
+}
+#endif
+
/*
* Architecture PAGE_KERNEL_* fallbacks
*
diff --git a/mm/mmap.c b/mm/mmap.c
index ca54d36d203a..6be9ff4007ab 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1721,6 +1721,9 @@ static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
if (file && is_file_hugepages(file))
return 0;

+ if (is_shadow_stack_mapping(vm_flags))
+ return 1;
+
return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
}

@@ -3370,6 +3373,8 @@ void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
mm->stack_vm += npages;
else if (is_data_mapping(flags))
mm->data_vm += npages;
+ else if (is_shadow_stack_mapping(flags))
+ mm->stack_vm += npages;
}

static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
--
2.21.0